Scroll type fluid displacement compressors are well known in the prior art. For example, U.S. Pat. No. 801,182 issued to Creux discloses such a compressor which includes two scrolls, each having an end plate and a spiral wrap or scroll element. The scrolls are positioned relative to each other so that the scroll elements interfit at an angular and radial offset to form compression spaces, namely, fluid pockets sealed off by the end plates and by the side walls of the scroll elements. By driving one of the scrolls in an orbital motion without rotation of the scrolls, the fluid pockets are moved toward the center of the scroll elements thereby compressing the fluid pockets.
An axial seal mechanism generally is employed to seal off the fluid pockets in the axial direction. Such an axial seal mechanism usually include seal elements disposed on the axial ends of the scroll elements of both scrolls to seal off the gap between the axial end surface of each scroll element and the end plate adjacent the axial end surface. The seal elements are disposed in grooves formed along the axial end surfaces of the scroll elements. Two types of seal mechanisms have been used in scroll compressors.
The first type of seal mechanism is shown in Public Disclosure of Japanese patent application No. 51-117304 and Public Disclosure of Japanese Utility Model No. 57-83293. In these applications the seal elements of both scrolls move axially within their respective grooves. These seal elements are urged against the end plates by a spring disposed in the bottom of the groove or back pressure from the compressed fluid between the scrolls.
The second type of seal mechanism is shown in Public Disclosure of Japanese Utility Model No 57-180182. Each of the seal elements of this seal mechanism are first placed between the bottom of the groove and the end plate, and then deformed by compression during assembly to fill the gap bewteen the scroll element and the end plate. Both seal elements extend between the bottom of the grooves and the opposing end plates.
In both the first and second types of seal mechanisms, the axial end surfaces of the scroll elements and the opposing end plates must not contact each other. It is important to maintain an axial gap between them to allow for heat expansion and prevent excessive wear to the scrolls.
In the first type of seal mechanism, since both seal elements can move a limited distance in the axial direction, it is difficult to set the elative axial location of both scrolls. When the axial end surface of the scroll element of one scroll is placed directly against the end plate of the other scroll without a gap between them, the seal elements cannot move axially, and the seal elements cannot function. Accordingly, an axial gap between the scrolls is necessary, but this axial gap makes it difficult to assemble the compressor. Also, since the scrolls must maintain a predetermined axial position during operation, additional mechanisms are required which complicate the construction of the compressor.
Also, in the second type of seal mechanism, since both seal elements are disposed between the bottom of the groove of the scroll element and the opposing end plate, high precision is required in the manufacture of the seal elements and each part of the scrolls. Hence, it is difficult to produce a scroll compressor.